ECP-CI study of electronic structure and geometry of small neutral and charged Ag n clusters; Predictions and interpretation of measured properties

Bonačić‐Koutecký, Vlasta; Češpiva, L.; Fantucci, P.; Koutecký, J.

doi:10.1007/bf01429171

Cited by 27 publications

(13 citation statements)

References 8 publications

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“…According to ab initio calculations, the binding energy of Ag 2 ͑i.e., the excess energy of the process AgϩAg→Ag 2 ͒ amounts only to 1.6 eV, 14 and hence an Ag 2 * species which subsequently decays into Ag 2 by emitting a photon with hϭ2.6 eV ͑ϭ476 nm͒ is not feasible. Obviously the energy balance can only be fulfilled if a larger number of bonds is formed, that means if larger clusters are involved.…”

Section: Discussionmentioning

confidence: 98%

Light emission during the agglomeration of silver clusters in noble gas matrices

Rabin

Schulze

Ertl

1998

The Journal of Chemical Physics

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The agglomeration of small silver clusters in noble gas matrices to form larger ones may be accompanied by the emission of light. Spectral analysis reveals that part of radiation intensity can be attributed to fluorescence from excited metal atoms, dimers and trimers the formation of which results from cluster/cluster agglomeration as a consequence of the gain in binding energy. The remaining spectral features must be assigned to excited clusters Agn, with n⩾4.

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Section: Discussionmentioning

confidence: 98%

Light emission during the agglomeration of silver clusters in noble gas matrices

Rabin

Schulze

Ertl

1998

The Journal of Chemical Physics

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“…A qualitative consideration of the differences in the ionization potential (IP) values of silver clusters and of Trp provides a guidance to find low‐energy CT electronic states likely to occur for low values of the IP differences. In addition to atomic Ag, this might be the case for silver clusters with an even number of atoms ( n =2,4,6,8), which are more stable than those with an odd number of atoms 36. The ultimate aim is to explore optical properties of silver–tryptophan complexes, without complications due to the environment, as prototypes for nanoparticle–biomolecule hybrid systems.…”

Section: Discussionmentioning

confidence: 99%

Optical Properties of Gas‐Phase Tryptophan–Silver Cations: Charge Transfer from the Indole Ring to the Silver Atom

et al. 2006

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We present a joint experimental and theoretical investigation of the electronic excitation spectra of the tryptophan-silver complex. The photodissociation spectrum of gas-phase [Trp-Ag]+ was measured from 215 to 330 nm using a quadrupole ion trap coupled to an optical parametric-oscillator laser. The calculated time-dependent density functional theory (TD-DFT) absorption spectra for different prototypes of structures are presented. Low-energy transitions that are experimentally observed are only calculated for the charge-solvation (CS) structures. These transitions are a signature of the metal-pi interaction in [Trp-Ag]+. The recorded spectrum is compared to a Boltzmann average of the absorption spectrum obtained from direct molecular dynamics (MD) simulations involving simultaneous transitions to excited states based on semiempirical configuration interaction (CI) calculations. The results demonstrate that charge transfer can be photoinduced from the indole ring to the silver atom.

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“…The ground state geometries of Ag n clusters have been calculated [34], and the two lower energy structures of Ag 8 (T d and D 2d symmetry) are the same as those of Na 8 , for which a complete analysis of the excited state has been published and compared with the measurements of Baumert et al [35]. It is clear from the analysis done for Na 8 that the oscillator strength of different excited states varies much from one state to the other, some transitions being forbidden for symmetry reasons.…”

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confidence: 99%

Ag8Fluorescence in Argon

et al. 2001

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The fluorescence of Ag 8 in an argon matrix and in argon droplets is reported. This is the first unambiguous assignment of the fluorescence of a metal cluster larger than the tetramer, indicating that the excited state lifetime is longer than previously thought. It is discussed as a possible result of a matrix cage effect. The excitation spectrum is compared with two-photon-ionization measurements of Ag 8 in helium droplets and to known absorption data. The agreement is excellent. We propose that the excited states relax rapidly through vibrational coupling to a long-lived state, from which the fluorescence occurs. DOI: 10.1103/PhysRevLett.86.2992 Optical spectroscopy has proven to be a powerful tool for understanding the electronic structure of atoms and molecules. Over the past decade these techniques have also been applied very successfully to metal clusters. Small metal clusters have been investigated in free beam experiments, using techniques such as resonant two-photon-ionization (R2PI) spectroscopy [1,2], laser-induced fluorescence [3], and pump-probe [4,5] techniques. Fragmentation becomes, however, more important as the cluster size increases and nondissociative electronic excitation processes have not been observed for free metal clusters larger than trimers [6]. Photodepletion spectroscopy was therefore used to measure optical absorption spectra of free metal clusters larger than three atoms [7][8][9].Also the fluorescence lines of free metal clusters are expected to be observed only for very small clusters. Wöste and co-workers have shown that, in the case of K 3 , the fragmentation of optically excited clusters occurs within a few hundred femtoseconds [10]. This is much shorter than the characteristic time scale necessary for a dipole transition and therefore no fluorescence can be observed in this case.Alternatively, optical absorption measurements of matrix isolated and mass-selected silver clusters have been performed for sizes up to n 39 [11]. No signal decrease has been observed over time, so it is clear that the matrix is effectively preventing the clusters from dissociating. This so-called cage effect is well known for molecules in a gas atmosphere or in a liquid. In the case of I 2 , for example, it has been shown that a single rare gas atom adsorbed on the molecule hinders the photofragmentation and allows the fluorescence [12].This opens the possibility of observing fluorescence for small metallic clusters if the excited state of the particle has a sufficient lifetime for a radiative transition to take place. However, with increasing size the competition between the different possible relaxation processes (vibrations, fluorescence, fragmentation) increases and, due to their shorter characteristic time, the radiationless relaxation processes are expected to quench the fluorescence [13][14][15].In the case of silver, fluorescence of Ag 3 and, more recently, Ag 4 has been unequivocally determined. A number of hitherto unidentified emission bands have been observed in the studies of non-mass-s...

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ECP-CI study of electronic structure and geometry of small neutral and charged Ag n clusters; Predictions and interpretation of measured properties

Cited by 27 publications

References 8 publications

Light emission during the agglomeration of silver clusters in noble gas matrices

Light emission during the agglomeration of silver clusters in noble gas matrices

Optical Properties of Gas‐Phase Tryptophan–Silver Cations: Charge Transfer from the Indole Ring to the Silver Atom

Ag8Fluorescence in Argon

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